It is known that, in general terms, artificial turfs, in particular for sports fields, consist of a synthetic mat formed by a sheet substrate in which there extend vertically filaments which simulate a natural greensward; infill materials are arranged between the filaments to form one or more filling layers; the infill materials most commonly used are sand and relatively elastic polymeric materials (mainly natural or synthetic rubber, but also thermoplastic materials of various types), which are either mixed together or arranged in layers, according to various methods.
U.S. Pat. No. 4,735,825 and EP-A-174755 disclose artificial turf structure including as an infill material cork granules and peat-based materials respectively.
WO2006/08579 discloses a mixed turf (i.e. a turf including both synthetic and natural grass filaments) wherein a layer of organic material, suitable for the development of living plants, is used in combination with a traditional infill material layer.
The known infill materials are not all entirely satisfactory under various aspects, for example in terms of performance, costs, draining capacity and humidity maintenance.